Wednesday 28 August 2013
Pancreas FNA; pancreatic fine needle aspiration
Accurate preoperative diagnosis of pancreatic lesions is crucial for proper clinical management. Routine tissue diagnosis with laparotomy or core needle biopsy is seldom performed due to significant morbidity and potential mortality. In addition, core needle biopsy may have potential risk of needle tract tumor implantation.
Fine needle aspiration (FNA) has been increasingly used in the diagnosis of pancreatic lesions because of relatively high diagnostic performance and low complication rate.
FNA biopsy of pancreatic lesions can be performed via a percutaneous transabdominal or endoscopic approach. Transabdominal biopsy is performed under the guidance of either ultrasound or computed tomography (CT).
With the development of linear array echoendoscopy, endoscopic ultrasonography guided FNA (EUS-FNA) has become the choice of diagnostic approach in most institutions. Dependent on the location of the lesion of interest, the biopsy can be performed via a transgastric or transduodenal route. A transduodenal approach is commonly used for the lesions located in the head or uncinate process of the pancreas. If the lesion is located in the body or tail, a transgastric approach is generally used. Recognition of gastric or duodenal epithelial contaminants can be essential to avoid misinterpretation during cytological evaluation of the specimens.
Dependent on the nature of pancreatic lesions, different diagnostic approaches may be employed. For solid lesions, a definite diagnosis is highly desirable and can be achieved by cytomorphologic analysis with or without ancillary studies.
To render a diagnosis of pancreatic neoplasms other than ductal adenocarcinoma, adjunct ancillary studies including immunocytochemistry may be required.
Rapid on-site evaluation during the procedure helps ensure adequate sampling and appropriate specimen triage. If there are grossly visible particles in the needle rinse from an FNA pass that shows diagnostic cells on rapid smears, cell blocks are highly likely to contain diagnostic tissue fragments.
If the lesion is cystic, EUS-FNA primarily serves as a tool for risk assessment, identifying the lesions with high grade dysplasia or malignant potential that may require surgical intervention. To achieve this goal, an integrated approach that combines imaging studies, cytomorphologic evaluation, cyst fluid analysis and molecular tests is recommended.
For solid pancreatic neoplasms, terminology similar to that used in the histopathology is preferred. For cystic lesions, a descriptive diagnosis may be acceptable.